Prevention of blow-by in cavitated assemblies



R. L. OLSON 2,863,186

PREVENTION OF BLOW-BY IN CAVITATED ASSEMBLIES Dec. 9, 1958 Filed May 23, 1956 Rw/Zm/ L. 0/503" Unite States Patent PREVENTION OF BLOW-BY IN CAVITATED ASEMBL1ES Richard L. ()lson, Chicago, Ill.

Application May 23, 1956, Serial No. 586,738

11 Claims. (Cl. 2210) The present invention relates to improvements in the sealing of cavitated assemblies and is particularly concerned with means for elfectively sealing opposed mating surfaces or faces of sand core boxes, pressure molds, blow plates and mating flasks or molds and other enclosures where sealing against internal pressures is required.

In a typical sand core blowing assembly, for example, two or more confronting mold members are clamped or pressed together, and a stream of air and sand particles, including a suitable binder, is blown into the cavity defined by the cooperating sections under substantial air pressure. The abrasive character of the sand makes it imperative to provide a completely air tight seam at the junction between the cooperating mold sections. Otherwise, the condition known as blow-by exists in which the 0 high velocity, high pressure air stream is forced through minute discontinuities between the mold sections. Within a surprisingly short time, the continued blow-by severely erodes the mating surfaces of the core box necessitating removal of the core box from the production line and refacing the box in the eroded areas, or otherwise patching up the damage done by the erosion. The cost of maintenance on core boxes thereby becomes quite high and their useful life uneconomically low.

An elastic seal that is tongue and grooved in the parting faces of the confronting members of a core box is the most satisfactory expedient available for preventing blow-by. ideally, the confronting faces of the mold members should be in perfect juxtaposition about the cavity. However, such juxtaposition is difiicult to attain and 5 even more difficult to maintain, due in the first instance to machining tolerances, and in the second instance to warpage factors. Therefore, there may be a tendency for air and sand to ride or travel along the flexible seal and into the groove into which the seal carried by one of the mating core box members fits in the other of the core box members. In some instances, the air may actually force its way over and around the seal under prolonged blowing pressure. Due to such tendency in such areas or sections of the seal, cross-over erosion may take place.

Another problem encountered in the use of such an elastomeric blow-by seal resides in blowing cores into open end split core boxes, where there is a tendency for air and sand to blow across the core box face that meets or is engaged by the blow plate of the blowing machine. It has been found that there is a tendency for the air to enter the chamber or groove into which the tongue portion of the seal fits, by compression of the compressible elastomeric material of the seal and thereby carrying sand down into the groove. This causes erosion of the 55 groove and also the adjacent core box parting or interface.

It is accordingly an important object of the present invention to overcome in an efiicient, practical, simple manner the foregoing problems, as well as in other ways to improve the elastomeric sealing of separable enclosures such as core boxes and the like which are cavitated to receive within the cavities thereof fluent material or must at least maintain internal pressures against blow-by.

Another object of the invention is to provide an improved sealing structure against blow-by from cavitated separable assemblies. 7

A further object of the invention is to provide an elongated blow-by seal structure with improved means for preventing escape of fluid thereby.

A still further object of the invention is to provide improved means for preventing entry of fluid into the end of a seal groove in open ended split mold members presenting an end face for engagement by a blow plate or the like.

Still another object of the invention is to provide improved means for assuring complete engagement of a flexible seal in a groove of a separable mold member in which the seal is attached, and freedom from air pockets or areas of separation.

Other objects, features and advantages of the present invention will be readily apparent from the following detailed description of a preferred embodiment thereof taken in conjunction with the accompanying drawing in which:

Figure 1 is an isometric view partly in section, of one half of a separable core box structure;

Figure 2 is an isometric view of the remaining half of the core box structure, also partly in section;

Figure 3 is an enlarged fragmentary sectional detail view taken substantially on the line III-Ill of Figure 1; and

Figure 4 is a fragmentary enlarged sectional detail View taken substantially on the line lV-IV of Figure 1.

By way of example of a cavitated assembly embodying features of the invention, a sand core box structure is shown in Figures 1 and 2 comprising separable, complementary core box members 5 and 7 having, respectlvely, opposed faces which in assembly are adapted to fit in juxtaposition and provide therein matching halves of a core cavity identified at it) and ll, respectively. In the present instance, the core box assembly is of the type known as an open end split core box wherein the opposite ends of the core cavities l0 and It have respective run-out channels or grooves 12 from the opposite ends of the core cavities through the respective oppos1te ends of the core box members or sections 5 and 7. When the core box members 5 and 7 are assembled in face-to face relation, the run-out channels or grooves 12 match to provide openings at the opposite ends of the core box into the core cavity.

In the assembled relationship of the core box members 5 and 7 ready for blowing a sand core into the cavity 10, 11 thereof, the lower end of the core box is placed upon a smooth, flat surface 13 which may be a bed or plate provided under a core blowing machine blow plate which is clamped or pressed down on the oppositeor upper end of the core box assembly with a blow orifice from the blow plate over the upper of the holes provided by the matching complementary run-out channels 12 on the upper end of the core box. When the blowing machlne is operated the core box cavity is filled inclusive of the run-out openings at the opposite ends of the core box assembly. Suitable screened vents 14 from the core box cavity provide for exhaust of the air by which the sand core is blown into the cavity.

In order to prevent blow-by at the interface joint about the core box cavity sealing means are provided, herein comprising a sealing strip 15 located as closely as practicable to the cavity and the present instance in view of the open ended nature of the cavity one such sealing strip being disposed on each side of the cavity. It will be understood, of course, that if. the core box were of the type having an enclosed cavity, that is not open at the opposite ends, or open only at one end, the sealing strip 25 would be continuous entirely about the cavity.

Herein the seal ldcomprises an elastic material of suitable nature and which may originally be a synth natural plastic substance of which various elastome.s have been found especially satisfactory. For example, a synthetic rubber of the Buna'l l type modi c resistance to hydrocarbons such as her 1 type copolymers, where hydro-carbon oils are 2 or elastomers of the polymerized chloroprene are suitable for the present purpose. These materials lend themselves well to formation of the seal in situ within a seal chamber provided by res ective opposing, generally registering, confronting grooves 17 and 18 formed within the respective joint faces 8 and 9 of the core box members (Fig. 4). it will be observed that while both of the grooves 17 and it; are of substantial depth, the groove l? is somewhat wider than the groove and the groove l3 is of substantially truncated, that is flat bottom, V-shape.

Molding of the seal 15 is effected by placing Within the chamber provided by the grooves 17 and 18, the core box members 5 and 7 being assembled together, an uncured strip of the seal material, indicated in Fig. 4 by the dash outline S. This strip contains in its formulation blowing agent of a decomposable compound which will liberate a gas such as nitrogen and/or ammonia under the conditions employed in curing or vulcanization of the clastomer. Such blowing agent, in the presence of the heat of vulcanization causes expansion of the material by formation of a large number of individual small bubbles in the elastomer providing a closed cell structure, without connected pores. Furthermore, by the inclusion of the blowing agent, the sealing material is caused to expand and fill the chamber provided by the matching grooves.

Prior to inserting the strip S into the seal chamber, the surfaces defining the groove 17 are treated with a bonding agent, so that after curing has been completed the seal S will be permanently bonded or secure-d into the groove 17. On the contrary, the surfaces of the groove are treated with an anti-sticking or bond-preventing material such as a silicone separator, or a suspension of super-fine mica particles or graphite in a vaporizable vehicle such as alcohol or in a silicone wash is applied to the walls of the groove 18, before curing of the seal. Therefore, aftercuring, the seal 15 remains permanently bonded Within the groove l7 and readily separates from the groove 18, although due to having been formed intimately within the grooves, the seal conforms intimately with the surfaces defining the groove 13. It is also found that after curing the exposed surfaces of the seal 15, that is the surfaces outside of the groove 17 have a tough, air impervious skin.

It may also be noted that in order to assure positive ejection of air from within the groove 3.7 during the curing and expansion of the seal material therein, it has been found desirable to provide the groove 17 within which the seal is fixed with side walls that have oblique fillet junctures 19 with the inner or base wall of the groove. As will be observed in Pig. 4-, through this arrangement the uncured strip S engages not only in the bot tom or root of the groove 17 but also the oblique fillets 19 so that as curing and expansion progresses, air within the groove about the strip S may easily escape and be ejected from the groove whereby to assure as nearly as practical perfect bonding of the sealing strip within the surfaces defining the groove i7. Within the groove 13, the antibonding agent or material used therein, and also along the margins of the core box member face 9 adjacent the groove 18 facilitates ejection and escape of air from within the groove 18.

During a core blowing operation, sand and binder are blown under substantial air pressure by the blowing machine into the core box cavity. Any air that may tend to escape through the mating or interface joint between the opposing core box member faces 3 and 9 encounters the resilient seal 15 and is stopped or turned back. It will be appreciated that because of its resilient, flexible elastic nature, the tendency of the seal 15 is to hug the wall of j the groove 18 on the opposite side from the pressure against the seal with greater sealing pressure proportionate to the air pressure exerted against the seal during core blowing. Thereby escape of pressure from the core box cavity is prevented.

However, in the open end split core boxarrangem'ent as exemplified herein, there is a tendency for the air and sand to blow across the end face of the core box against which the blow plate is pressed and thus enter the groove 18 of the seal chamber. In order to prevent such entry of air and sand, respective cap enlargements 20 are provided at the respective ends of each of the seal strips 15. These caps 2d are formed from the same material as the seal strips and are molded integrally in one piece therewith. To accommodate the caps 2f the end faces of the core box member 5 in line with the seal grooves 17 therein are provided with cap enlargement recesses 21, while the end faces of the core box member 7 in line with the seal grooves 18 are provided with cap accommodating recess enlargements 22. It will be observed that at the inner sides defining the recesses 22 are respective outwardly facing wall surfaces 23 against which the end caps 20 fit in intimate separable engagement in the assembly and toward which the end caps are resiliently pressed with proportionately greater pressure as the core blowing pressure increases. Thereby the ends of the grooves 18 are sealed against entry of air and sand from the ends of the core box. In the present instance, of course, either end of the core box assembly may be brought into blowing relation to the blow plate of the core blowing machine.

Since due to virtually inevitable irregularity in the core box faces 8 and 9 there may be at some point more tendency for movement of air and sand between the parting faces toward the seal 15, and due to the high velocity perhaps a tendency to ride or travel over the peak or crown or the seal 15 within the groove 18 and then pass the opposite side, means are provided by the present invention to stop any such tendency toward riding over or traveling over the seal. Herein this is accomplished by providing the seal 15 at suitable intervals with transverse fingers or barriers 25. These barriers 25 may be spaced apart longitudinally of the seal strip 15 as far apart or as close together as may be deemed expedient, dependiii'g upon proximity to the point of fluid pressure entry into the core box or other cQnsidt' JraIio'ns that may indicate possibility of movement of air and sand longitudinally of the seal. For example, as shown in Figure 1, one of the safety barriers 25 is located near each end portion of the seal member 15, adjacent to the end opening portions 12 of the cavity and another of such safety barriers or fingers 25 is located intermediate the endwardly located safety barriers. However, in different types of core boxes, location of the safetybarriers 25 may be determined to be further apart or closer together and in some instances omitted in certain stretches and provided in other stretches or lengths of the seal strip as found to be or deemed to be desirable.

In a preferred construction, the safety barriers or fingers 25 are provided as integrally molded in one piece parts of the sealing strip structure 15 as a transverse or lateral fin formation. To this end, there are provided at the intervals along the base or retaining groove 17 laterally ofiset groove portions 27 to provide for the base portions of the barrier fins 25. correspondingly, the groove 18 has matching transverse barrier fin accomr'no dating lateral offsetextensions 28. Through this arrangement, the barrier fins 25 are formed incident to the formation of the seal 15 in the manner hereinbefore described.

It will be noted that by preference the barrier fins 25 extend to a crown height slightly greater than the crown height of the main portion of the sealing strip 15. Moreover, it should be noted that preferably the barrier fins asesnse extend to a greater width, that is ofiset distance from the adjacent side of the strip 15 at the inner side of the strip than at the outer side. Actually that portion of the barrier fins at the inner side of the sealing strip is the more important.

As a graphic illustration of the operation of the barrier fins 25, there have been applied to Figure l directional arrows 29 which indicate how air introduced into the core box cavity during blowing in of sand and possibly finding its way through the parting joint toward the seal member 15 tends to flow longitudinally along the sealing strip until it strikes one of the barrier fins 25 and is thereby deflected inwardly toward the core box cavity. Should there be any tendency of the air to move onto or over the crown of the sealing strip 15, it will encounter the crown projection of the barrier fin 25 in its path to be thereby deflected in toward the core cavity. As a result, it has been found in practice that any tendency for the air to ride over or escape past the sealing strip 15 is prevented.

it will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

I claim as my invention:

1. In an assembly including a pair of mating members defining a pressure differential cavity therein with confronting grooves in joint faces of said members providing a seal chamber space adjacent to said cavity, said grooves having respective confronting lateral offset barrier fin portions that extend in planes across the axes of the grooves, and a seal in said chamber space and said barrier fin ofi set portions of a material molded into intimate conformity and filling said sealing chamber space and said lateral offset spaces and thereby sealing the joint between said faces against pressure transfer both transversely and longitudinally of the seal.

2. In a cavitated assembly having members each with a joint face and confronting seal grooves in said faces, a blow-by seal in said grooves comprising a sealing strip disposed across the joint and provided with a transverse barrier fin projecting integrally laterally therefrom and operable to stop longitudinal movement of pressure fluid therealong.

3. in a cavitated assembly including a pair of separable members defining a cavity and with mating surfaces providing a joint therebetween, said surfaces having opposed matching grooves running alongside and adjacent to the cavity in said members, said grooves having matching laterally offset barrier spaces opening as pockets therefrom, and a seal against fluid passage transversely of the grooves filling said grooves and aflixed in one of said grooves and separable relative to the other of said grooves and having projecting integrally laterally therefrom a barrier fin in said barrier spaces to stop longitudinal movement of fluid under pressure therealong.

4. In a cavitated assembly such as a split sand core box, a blow-by seal including a seal strip sealingly disposed in generally registering grooves in the joint between the separable members of the cavitated assembly, said strip having a barrier fin projecting integrally laterally therefrom for interrupting fluid movement longitudinally of the seal strip.

5. In a cavitated assembly including a pair of members for face-to-face abutment with opposed cavity recesses in the members, the opposed faces of the members having blow-by seal grooves therein adjacent the cavity recesses and with the opposed grooves defining a seal chamber, said grooves having lateral pocket-like matching recesses therefrom, and an elastic seal filling said grooves and said lateral recesses, with that portion of the seal in said lateral recesses providing a barrier fin projecting integrally laterally therefrom for interrupting longitudinal travel of pressure fluid along the seal.

6. In a cavitated assembly including a pair of members for faceto-face abutment with opposed cavity recesses in the members, the opposed faces of the members having opposed blow-by seal grooves therein adjacent the cavity recesses and with the opposed grooves defining a seal chamber, said grooves having lateral pocket-like generally registering recesses therefrom, and an elastic seal filling said grooves and said lateral recesses, with that portion of the seal in said lateral recesses providing a barrier fin projecting integrally laterally therefrom for interrupting longitudinal travel of pressure fluid along the seal, said seal being separable with respect to one of said grooves and the barrier fin recess in said groove being deeper than the root of the groove so that the barrier fin extends to a greater height than the crown of the seal.

7. In a cavitated assembly comprising separable members with an open ended cavity therebetween, said members having separably opposed interfaces with confronting sealing grooves therein and running out at the end of the assembly from which said cavity opens, a blow-by preventing seal across the interfaces of said members and anchored in the grooves of one of said members and separable relative to the grooves in the other of said members, said seal running out at said end of the assembly, and a sealing-cap on said seal at said end to prevent entry of pressure fluid along said seal from said end.

8. In a cavitated assembly comprising separable members with an open ended cavity therebetween, a blow-by preventing seal across the interfaces of said members and anchored in one of said members and separable relative to the other of said members, said seal running out at the end of the assembly through which the cavity opens, and a sealing cap on said seal at said end to prevent entry of pressure fluid along said seal from said end, said members being recessed at said end of the assembly to accommodate said cap.

9. In an open end split core box assembly comprising cavitated core box members having abuttable separable faces and defining therebetween a core cavity opening through one end of the assembly for filling by means of a core blowing machine, a flexible sealing strip extending across the joint provided by said faces adjacent to the core cavity and running out at said end of the assembly, said sealing strip having an end cap and intermediate its length a laterally projecting integral barrier fin.

10. In a method of sealing a cavitated separable assembly of members providing therebetween a separable joint with portions of the members alongside the cavity dis posed in face-to-face relation and subject to pressure differential between the cavity and the external aspects of the assembly tending to effect blowing through the joint, providing in the face of one of said members a generally quadrilateral seal receiving groove, providing in the other of said members a seal receiving groove confronting the first mentioned groove and providing therewith a seal chamber, forming the root in the first of said grooves generally flat but with oblique fillets, treating the second mentioned groove with an anti-bonding agent, placing the members in face-to-face relation with a strip of uncured heat curable and expandable and settable elastic sealing material in the chamber provided by said grooves, the cross-sectional mass of said strip being less than the crosssectional volume of said chamber, and curing the sealing material by subjecting the same to curing heat to expand within said grooves and fill said chamber by displacing air from the chamber.

11. In a cavitated assembly including members which in assembly define a cavity and have opposing joint faces,

said members having adjacent to the cavity therein opposed confronting grooves defining together a seal chamber, and a seal filling said chamber and comprising an expandable settable elastic material, one of said grooves being of generally quadrilateral form but having a root portion joined to the side walls of such groove by oblique fillets and the width of said one of the grooves being substantially greater than the remaining groove so that the 56516 5156866 tli'e'lfiafgifi of the joint face at each side of said remaining groove;

8 Wellman Oct. 29, 1946 Rehklau June 6, 1950 Coffey Sept. 25, 1951 Rodgers Ian. 12, 1954 Moore Mar. 30, 1954 Moore Dec. 20, 1955 Talalay Jan. 24, 1956 Orr May 8, 1956 Moore June 19, 1956 OTHER REFERENCES Foundry, September 1951, page 166. 

